The invention described herein may be manufactured and used by or for the Government of the United States of America for government purposes without the payment of any royalties therefor.
Gas turbines, including those used for propelling military vehicles, include two or more opposed bearings which must be continuously lubricated during gas turbine usage. This is accomplished by means of a lubricating system which provides the bearings with a lubricating fluid, such as natural or synthetic oil, to not only lubricate the bearings but to also provide for cooling.
When the gas turbine is shut down after usage, the residual heat from the turbine (which may be hundreds of degrees Fahrenheit) soaks back to the bearings leading to a possible coking condition. This is even more pronounced if there is insufficient engine idle time before turbine shut down. Basically, coking is the result of the lubricant becoming an oxidized solid oil deposit on the bearing surface and in the lubricant delivery system that can lead to insufficient lubricant supply to the bearings. This can result in engine seizure and/or a requirement for a complete engine overhaul, which is undesirable, particularly in tactical combat situations.
Accordingly, it is a primary object of the present invention to provide apparatus which flushes away the coked lubricant in rotating machinery bearings, particularly, in gas turbines which shut down at high temperatures.
A flushing system for removing lubricant coking in a turbine bearing, within a bearing housing having a fluid inlet and fluid outlet, includes a plurality of fluid containing tanks, at least a first of which contains a coking solvent, a second of which contains a cleaner and a third of which contains a lubricant. First and second couplings are provided with a first coupling being connected to the fluid inlet and the second coupling being connected to the fluid outlet, of the bearing housing. A supply pump has an outlet connected to the first coupling, and a return pump has an inlet connected to the second coupling. A first valving arrangement is connected between the tanks, and an inlet of the supply pump, and is operable to provide fluid from a selected one of the tanks to the supply pump for delivery to the bearing housing. A second valving arrangement is connected between an outlet of the return pump and the tanks, to supply return fluid from the bearing housing to the particular tank selected by the first valving arrangement.